1. Field of the Invention
The present invention relates to integrally woven multi-layer angle interlock fabrics, and more particularly to such fabrics which are woven so as to have a plurality of apertures within the thickness thereof extending along the width or length thereof.
2. History of the Prior Art
It is known in the art of integrally woven multilayer materials to weave a fabric from a plurality of different yarn systems which provide the fabric with multiple interwoven layers or plies of thickness. Fabrics of this type are illustrated by U.S. Pat. No. 3,749,138 of Rheaume et al., which patent issued Jul. 31, 1973 and is commonly assigned with the present application. The Rheaume et al. patent describes the weaving of a multi-layer fabric which is comprised of angled warp yarns extending through the thickness of the fabric and interwoven with fill yarns which extend across the width of the fabric in an orientation generally parallel to one another and to the opposite broad surfaces of the fabric and perpendicular to the warp yarns. A third or stuffer yarn system may be present such that generally parallel stuffer yarns extend along the length of the fabric in orientations perpendicular to the fill yarns.
Further examples of multi-layer woven fabrics are provided by U.S. Pat. No. 4,312,913 of Rheaume, which patent issued Jan. 26, 1982. The Rheaume patent illustrates fabric produced by an angle weave in which lengths of fill yarn disposed in a nominally parallel configuration are interwoven with angled warp yarns. The warp yarns extend in a zig-zag configuration through the thickness of the fabric between the opposite broad surfaces thereof so as to form a succession of intersecting warp sheets or layers. The warp sheets intersect with and form acute angles with the opposite broad surfaces of the woven fabric and with yarn layers formed by the fill yarns.
The multi-layer woven fabrics described in U.S. Pat. No. 3,749,138 of Rheaume et al. and U.S. Pat. No. 4,312,913 of Rheaume are typical of woven angled fabrics in which the warp yarn system extends through the entire thickness of the fabric to provide an integral, tightly woven multi-layer fabric having generally uniform properties throughout the thickness thereof. Such configurations are advantageous for many applications calling for multi-layer fabrics with good structural and other properties. Such fabrics have formed the basic configurations from which special fabric configurations have been designed for special applications. For example, the woven fabrics can be impregnated with a resin system which, when cured, results in a relatively rigid structural member of desired shape and having particular properties with respect to such things as strength, thermal conductivity, and electrical conductivity. Such fabrics have been woven so as to have partial slots within the opposite side surfaces thereof. The partial slots define opposite flaps in the fabric which provide the fabric with an I-beam configuration upon impregnation and curing.
Rigid structures can also be formed using such woven fabrics in other kinds of matrixes. For example, the fabric can be formed of and/or combined with matrices such as ceramics, glass, carbon, or metal in forming a rigid matrix having desired properties.
Further examples of integrally woven multi-layer angle interlock fabrics are provided by copending application Ser. No. 07/232,450 (now U.S. Pat. No. 4,958,663) of Miller et al., "WOVEN MULTI-LAYER ANGLE INTERLOCK FABRICS AND METHODS OF MAKING SAME", which application was filed Aug. 15, 1988 and is commonly assigned with the present application. The Miller et al. application describes a fabric woven so as to have a slot within the thickness thereof and extending along the length of the fabric. Because the fabrics described in that application are woven so that the warp yarns extend along the fabric in generally parallel, spaced-apart yarn layers or plies with the fill yarns extending through the thickness of the fabric between the opposite broad surfaces thereof in repeating fashion and interweaving with the war yarns, the fabric can be of virtually unlimited length or width as well as having advantageous structural properties in the length or width direction.
In spite of the variety of weaving techniques and configurations which have heretofore been used in the formation of integrally woven multi-layer angle interlock fabrics, such fabrics have been lacking in situations where it is desired to form a hollow, multi-apertured fabric having a plurality of interwoven layers on one or both sides of the apertures. An integrally woven multi-apertured multi-layer fabric would be especially advantageous, not only in terms of providing such fabrics with substantial thickness where desired, but also in terms of being able to incorporate desired strength and conductivity properties into the woven fabric. Heretofore, fabrics used in the formation of hollow, multi-apertured structures have been limited to non-multi-layer configurations in which a single layer of fabric extends between opposite single layers forming face sheets. Where one or both of the face sheets are built up into multiple layered configurations, the multiple layers are not interwoven with other portions of the fabric including the layers interconnecting the opposite face sheets, so that an integrally woven multi-layer fabric is not provided.